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(meteorobs) Where did the meteors go?
Hello folks,
Last night was pretty clear again, so I decided to do a session for the
3rd evening in a row. I observed from my backyard. Even though my LM was
only 6.0-6.2 and some clouds interfered, I was disappointed to see only
6 meteors in 2 hr Teff! Compared to the prior 2 nights of good activity,
this was quite a letdown. I guess its just due to random distribution of
particles at a low rate. Also, we are getting further away from the peak
date (1/17) of the DCA, which is the major non-SPO component now.
Just as last night, the only good meteor was a mag 2 DCA. However, this
one was odd, because it had a very short path (only 4° long) far away
from the radiant. It lasted such a brief time (~0.33 sec) that my first
reaction was that this was a "fast" sporadic, even though the trajectory
aligned perfectly with DCA. But, analyzing it more closely, it had an
angular velocity of 4°/0.33s = 12°/sec , which is about right for a slow
DCA.
Just out of curiousity, I calculated the likelihood of various observed
hourly rates of meteors expected from the poisson distribution, given my
overall average hourly rate over the past 3 evenings:
lambda = 28meteors/5hr = 5.6/hr
probability rate
----------- ----
0.4% 0/hr
2.1% 1/hr
5.8% 2/hr
10.8% 3/hr
15.2% 4/hr
17.0% 5/hr
15.8% 6/hr
12.7% 7/hr
8.9% 8/hr
5.5% 9/hr
3.1% 10/hr
I believe lambda may not be quite a constant, because of the decreasing
activity of DCA component, but this table should give a rough idea of
the likelihood of a given observed hourly rate early in the evening
around this time of January, with a LM between 6.0 and 6.6.
Sincerely,
Mike Linnolt
REPORT FOLLOWS:
------------------------------------------------------------------------
OBS: Mike Linnolt (LINMI)
DATE: Jan. 26, 2000
TIME: 0545 - 0748 UT (7:45pm - 9:48pm HST Jan 25/26)
LOC: Haiku, Maui, HI (20° 54' N, 156° 18m W)
ELEV: 250m
Conditions: Some clouds. Temp 65F. RH 50%. Winds very light.
METHOD: Paper
Observing Periods Summary:
==========================
# Period(UT) FOV Teff F LM DCA AHY CAN AA* SPO
---------- --- ---- - --- --- --- --- --- ---
1 0545-0646 05h +00 1.00 1.09 6.0 1 0 0 0 3
2 0646-0748 06h +00 1.00 1.05 6.2 1 0 0 0 1
(*AA = anti-apex)
Periods Detail:
===============
Period #1:
----------
Mag->_-3___-2___-1____0___+1___+2___+3___+4___+5___+6
-------+----+----+----+----+----+----+----+----+----+
DCA:...........................................1..... = 1
AHY:................................................. = 0
CAN:................................................. = 0
AA :................................................. = 0
SPO:......................................2....1..... = 3
DEAD TIME: 1 min
LM: 6.0
Note: Minor cloud cover, average 25% obstruction for 20 min.
Period #2:
----------
Mag->_-3___-2___-1____0___+1___+2___+3___+4___+5___+6
-------+----+----+----+----+----+----+----+----+----+
DCA:............................1.................... = 1
AHY:................................................. = 0
CAN:................................................. = 0
AA :................................................. = 0
SPO:...........................................1..... = 1
DEAD TIME: 2 min
LM: 6.2
Note: LM improved, cloud obstruction less than period #1, but
only half as many meteors were seen! The mag 2.0 DCA was
unusual. It had a short path (4°) 60° away from the radiant and
duration 0.33 sec. However trajectory, path length/radiant,
and velocity criteria all pass for shower association.
END OF REPORT.
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